CN103755604B - Hydrogen fluorine ether sulfone compound and preparation method thereof, lithium-ion battery electrolytes - Google Patents

Abstract

The invention provides a hydrofluoroether sulfone compound, a preparation method thereof, and an electrolyte for a lithium ion battery. The lithium ion battery electrolyte includes a lithium salt, a solvent, and a hydrofluoroether sulfone compound represented by formula (I). Compared with the prior art, the hydrofluoroether sulfone compound represented by the formula (I) added to the lithium-ion battery electrolyte of the present invention contains hydrofluoroether groups. Firstly, the hydrofluoroether sulfone compounds represented by formula (I) retain the advantages of high pressure resistance of sulfone compounds, which can improve the pressure resistance of the electrolyte; secondly, the hydrofluoroether group is beneficial to overcome the sulfone compounds It has the disadvantages of high melting point and viscosity, and has high conductivity; again, hydrofluoroether sulfone compounds have good compatibility with common solvents and lithium salts in electrolytes, and are easy to form a homogeneous solution; finally, the formula The hydrofluoroether sulfone compounds shown in (I) have the advantages of hydrofluoroether compounds, which are beneficial to increase the flash point of the electrolyte and make the electrolyte have good flame retardancy.

Description

Hydrofluoroether sulfone compound and preparation method thereof, lithium-ion battery electrolyte

technical field

The invention belongs to the technical field of lithium-ion batteries, and in particular relates to hydrofluoroether sulfone compounds, a preparation method thereof, and an electrolyte for lithium-ion batteries.

Background technique

Safety is a key issue restricting the development of large-capacity and high-power lithium-ion batteries. At present, organic carbonates are widely used as solvents in electrolytes of lithium-ion secondary batteries, super batteries and capacitors, such as propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), etc. Liquid has excellent electrochemical performance, but due to the disadvantages of low flash point (less than 30°C) and flammability of organic carbonate, the battery is extremely easy to catch fire or even explode under overcharge and overheating conditions. Therefore, in recent years, battery research has mainly focused on two aspects, one is to explore electrolytes with a higher flash point or even non-combustibility; Electrochemical window and electrode matching.

Ionic liquid has the characteristics of a safe electrolyte, that is, non-volatile, non-flammable, and has an electrochemical window greater than 5V, but it is difficult to obtain due to its high price, high viscosity and poor compatibility with electrode materials. substantive application.

Sulfone solvents have a wide electrochemical window (>5.8Vvs. Li ⁺ /Li), so they can be used as functional electrolyte additives or even solvents. However, sulfone compounds exhibit a high melting point and cannot form a stable SEI film on the negative electrode, resulting in attenuation of battery performance. At the same time, most sulfone compounds are solid at room temperature and can only be formed into liquids when mixed with other solvents. electrolyte.

The Chinese patent with publication number CN102780039A discloses a non-aqueous organic electrolyte for a lithium-ion secondary battery and a preparation method thereof. The components of the non-aqueous organic electrolytic solution include: non-aqueous organic electrolytic solution solvent, lithium salt, and additives, wherein the non-aqueous organic electrolytic solution solvent includes γ-butyrolactone and saturated cyclic ester; the additive includes: unsaturated cyclic Ester compounds, sulfone compounds. The non-aqueous organic electrolyte has a high flash point, which can effectively improve the high-voltage stability and high-temperature safety of lithium-ion secondary batteries, and at the same time, can effectively reduce the capacity of lithium-ion secondary batteries in long-term high-temperature storage loss, improving the overall performance of the lithium-ion secondary battery. However, due to the disadvantages of high melting point and high viscosity of sulfone compounds, it needs to be used with a co-solvent.

Hydrofluoroether products, such as chain hydrofluoroether and cyclic hydrofluoroether, have similar properties, that is, colorless, transparent, low viscosity, non-flammable, and are a very safe liquid. In the existing industrial market, it is mainly used as cleaning agent, desiccant and solvent.

The present invention aims to provide a new class of hydrofluoroether-modified sulfone compound-hydrofluoroether sulfone, which combines the advantages of hydrofluoroether products and sulfone products. Application in ion battery electrolyte. This kind of hydrofluoroether sulfone additive is used in lithium battery electrolyte, which can improve its thermal stability and pressure resistance, and provide a new technical solution for the development of large-capacity power lithium battery electrolyte.

Contents of the invention

In view of this, the technical problem to be solved by the present invention is to provide a hydrofluoroether sulfone compound, a preparation method thereof, and an electrolyte solution for lithium-ion batteries.

The present invention provides a hydrofluoroether sulfone compound, as shown in formula (I):

Wherein, R ₁ is a C1-C20 alkyl group; R ₂ is a C0-C20 alkylene group; R _f is a C1-C10 fluoroalkyl group.

Preferably, the R ₁ is a C1-C6 alkyl group.

Preferably, the R ₂ is a C1-C6 alkylene group.

Preferably, said; R _f is a C1-C4 fluoroalkyl group.

The present invention also provides a method for preparing hydrofluoroether sulfone compounds, comprising: under the action of the first catalyst, combining the sulfone compounds represented by the formula (II) with the fluorine-containing halide represented by the formula (III) Mixed reaction to obtain the hydrofluoroether sulfone compound shown in formula (I);

Or under the action of the second catalyst, mix and react the sulfone compound represented by the formula (II) with the fluorine-containing olefin represented by the formula (IV) to obtain the hydrofluoroether sulfone compound represented by the formula (I);

Among them, R ₁ is an alkyl group of C1-C20; R ₂ is an alkylene group of C0-C20; R _f is a fluoroalkyl group of C1-C10; X is a halogen; Rf ₁ and Rf ₂ are fluorinated alkanes or F , R ₃ and R ₄ are H, F, alkane or fluorine-containing alkane, and the fluorine-containing alkene represented by formula (IV) has the same carbon chain structure as Rf.

The present invention also provides a lithium ion battery electrolyte, comprising:

Lithium salt, solvent and hydrofluoroether sulfone compounds represented by formula (I);

Wherein, R ₁ is a C1-C20 alkyl group; R ₂ is a C0-C20 alkylene group; R _f is a C1-C10 fluoroalkyl group.

Preferably, the concentration of the lithium salt is 0.7-1.4 mol/L.

Preferably, the mass of the solvent is 1% to 80% of the mass of the lithium-ion battery electrolyte.

Preferably, the mass of the hydrofluoroether sulfone compound described in the formula (I) is 0.01% to 60% of the mass of the lithium-ion battery electrolyte.

Preferably, the solvent is selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, propyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, 1,2- One or more of dimethoxyethane, γ-butyrolactone, γ-valerolactone, tetrahydrofuran, 2-methyltetrahydrofuran, acetate, propionate, butyrate and ethylene sulfite kind.

The invention provides a hydrofluoroether sulfone compound, a preparation method thereof, and an electrolyte for a lithium ion battery. The lithium ion battery electrolyte includes a lithium salt, a solvent, and a hydrofluoroether sulfone compound represented by formula (I). Compared with the prior art, the hydrofluoroether sulfone compound represented by the formula (I) added to the lithium-ion battery electrolyte of the present invention contains hydrofluoroether groups. First, the hydrofluoroether sulfone compound represented by formula (I) retains the advantages of high pressure resistance of sulfone compounds, which can improve the pressure resistance performance of the electrolyte, and is especially suitable for the needs of high-power lithium batteries; secondly, The hydrofluoroether group is beneficial to overcome the disadvantages of high melting point and viscosity of sulfone compounds, so that the electrolyte can be applied in a lower temperature environment, and the electrolyte has a higher conductivity; again, the formula (I) The hydrofluoroether sulfone compounds shown have good compatibility with common electrolyte solvents and lithium salts, and are easy to form a homogeneous solution; finally, the hydrofluoroether sulfone compounds shown in formula (I) have both hydrofluorine The advantages of ether compounds are beneficial to increase the flash point of the electrolyte and make the electrolyte have good flame retardancy.

detailed description

The present invention provides a hydrofluoroether sulfone compound, as shown in formula (I):

Wherein, R ₁ is an alkyl group of C1～C20, preferably an alkyl group of C1～C12, more preferably an alkyl group of C1～C6, and more preferably an alkyl group of C1～C3; The group can also be a branched chain alkyl group, and there is no special limitation. _The present invention is preferably a straight chain alkyl group; R2 is an alkylene group of C0～C20, preferably an alkylene group of C1～C12, more preferably a C1～C12 alkylene group. The alkylene group of C6, preferably the alkylene group of C1～C3 again; The alkylene group can be straight chain alkylene group also can be branched chain alkylene group, there is no special limitation, preferably straight chain alkylene group in the present invention chain alkylene; R _f is a C1-C10 fluoroalkyl group, more preferably a C1-C8 fluoroalkyl group, and more preferably a C1-C4 fluoroalkyl group; There is no special limitation on the number of atoms, and it can be a partially substituted fluoroalkyl group or a perfluoroalkyl group; the fluoroalkyl group can be a straight-chain fluoroalkyl group or a branched-chain fluoroalkyl group. The alkyl group is not particularly limited, and it is preferably a linear fluoroalkyl group in the present invention.

The present invention further provides a method for preparing the hydrofluoroether sulfone compound represented by the above formula (I), which is carried out according to the following steps: under the action of the first catalyst, the sulfone compound represented by the formula (II) is combined with the sulfone compound represented by the formula (III ) to react the fluorine-containing halide compound represented by the formula (I) to obtain the hydrofluoroether sulfone compound represented by the formula (I).

Wherein, R ₁ is a C1-C20 alkyl group; R ₂ is a C0-C20 alkylene group; R _f is a C1-C10 fluoroalkyl group; X is a halogen. The R ₁ , R ₂ and R _f are the same as those described above, and will not be repeated here.

According to the present invention, the sulfone compound represented by the formula (II) is preferably prepared according to the following steps: first, the compound represented by the formula (V) is mixed with the compound represented by the formula (VI) under basic conditions performing a reaction to obtain a compound represented by formula (VII); then, mixing the compound represented by formula (VII) with hydrogen peroxide and performing a reaction to obtain a compound represented by formula (II).

Wherein, the R ₁ is a C1-C20 alkyl group; R ₂ is a C1-C20 alkylene group; X ₁ is a halogen, preferably Cl or Br, more preferably Cl. Both R ₁ and R ₂ are the same as those described above, and will not be repeated here.

According to the present invention, the synthesis of the compound represented by formula (VII) is carried out according to the following steps: under alkaline conditions, the compound represented by formula (V) is mixed with the compound represented by formula (VI), and the temperature rises for a certain period of time, and the product Purify again.

The basic conditions are provided by basic compounds, preferably alkali metal hydroxides, more preferably sodium hydroxide and/or potassium hydroxide.

The molar ratio of the compound represented by the formula (V) to the compound represented by the formula (VI) is preferably (1-1.3):1, more preferably (1-1.1):1.

Said reaction is under the condition of inert gas protection, preferably nitrogen protection;

The reaction is carried out by slowly adding the compound represented by the formula (VI) dropwise under heating. The temperature of the reaction is preferably 30°C to 40°C.

The reaction time is preferably 0.5-3 h, more preferably 1-2 h.

After the reaction is finished, a purification treatment is preferably carried out; the method of the purification treatment is preferably vacuum distillation.

The compound represented by the obtained formula (VII) is mixed with hydrogen peroxide for reaction, and the product is purified to obtain the compound represented by the formula (II). The reaction is preferably carried out by adding hydrogen peroxide dropwise to the compound represented by formula (VII) under vigorous stirring conditions; the reaction temperature is preferably 20°C to 30°C; the reaction time is preferably 8 ~20h, more preferably 8~14h.

The compound represented by the formula (VII) and hydrogen peroxide are preferably mixed in a molar ratio of 1:(1.5-3), more preferably 1:(1.8-2.2).

After the reaction is finished, the reaction product must be purified. The method of purifying treatment is preferably first to obtain the crude product by distillation, and then carry out rectification.

According to the present invention, the compound represented by the formula (I) can be synthesized according to the following method: under the action of the first catalyst, the sulfone compound represented by the formula (II) is reacted with the fluorine-containing halide represented by the formula (III), The hydrofluoroether sulfone compounds represented by the formula (I) are obtained. Wherein, the first catalyst is preferably a basic compound, more preferably an alkali metal hydroxide, and more preferably sodium hydroxide and/or potassium hydroxide.

In the present invention, the sulfone compound represented by the formula (II) reacts with the fluorine-containing halide represented by the formula (III), and the reaction is preferably carried out under vacuum conditions, and the reaction is more preferably carried out according to the following steps: Under the action of the first catalyst, add the sulfone compound represented by the formula (II) into the sealed reaction kettle, and after vacuuming, pass the fluorine-containing halide compound represented by the formula (III) into the reaction kettle, mix and react, The hydrofluoroether sulfone compounds represented by the formula (I) are obtained.

The molar ratio of the sulfone compound represented by the formula (II) to the fluorine-containing halide represented by the formula (III) is preferably 1:(1-2), more preferably 1:(1.2-1.5).

The reaction temperature between the sulfone compound represented by formula (II) and formula (III) is preferably 60°C-70°C; the reaction pressure is preferably 0.6-0.7MPa; the reaction time is 2-3h;

After the reaction is finished, the reaction product must be purified. The method of purifying treatment is preferably first to obtain the crude product by distillation, and then carry out rectification.

According to the present invention, the compound represented by the formula (I) can also be prepared by the following method: under the action of the second catalyst, the sulfone compound represented by the formula (II) and the fluorine-containing olefin represented by the formula (IV) are mixed and reacted .

Rf ₁ and Rf ₂ are fluorine-containing alkanes or F; R ₃ and R ₄ are H, F, alkane or fluorine-containing alkanes, and the fluorine-containing alkene shown in formula (IV) has the same carbon chain structure as Rf, that is, the formula ( The fluorine-containing olefin shown in IV) reacts with the sulfone compound shown in formula (II) to form the Rf substituent of the hydrofluoroether sulfone compound shown in formula (I).

According to the present invention, the reaction is preferably carried out according to the following steps: under the action of the second catalyst, add the sulfone compound represented by the formula (II) into the sealed reaction kettle, and after vacuuming, add the sulfone compound represented by the formula (IV) The fluorine-containing olefins are passed into the reaction kettle, mixed and reacted to obtain the hydrofluoroether sulfone compounds represented by the formula (I). The reaction temperature is preferably 60°C-70°C; the reaction pressure is preferably 0.3-0.4MPa; the reaction time is 3-4h.

Wherein, the second catalyst can be a catalyst well known to those skilled in the art, and there is no special limitation. In the present invention, it is preferably an alkaline compound, more preferably an alkali metal hydroxide, and more preferably sodium hydroxide and/or or potassium hydroxide; the first catalyst and the second catalyst can be the same compound or different compounds, and there is no special limitation; the mole of the sulfone compound represented by the formula (II) and the fluorine-containing olefin The ratio is preferably 1:(1 to 2), more preferably 1:(1.2 to 1.5).

After the reaction, it is preferred to wash with water, separate the phases, and purify the organic phase under the condition of vacuum distillation to obtain the hydrofluoroether sulfone compound represented by formula (I); it is more preferred to wash with water, and after phase separation, add bromine to the organic phase element, stirred for 1-4 hours, then added sodium thiosulfate solution to wash until neutral, separated phases, and rectified to obtain hydrofluoroether sulfone compounds represented by formula (I).

The present invention also provides a lithium-ion battery electrolyte, including: lithium salt, a solvent, and a hydrofluoroether sulfone compound represented by formula (I);

Wherein, R ₁ is a C1-C20 alkyl group; R ₂ is a C0-C20 alkylene group; R _f is a C1-C10 fluoroalkyl group. The R ₁ , R ₂ and R _f are the same as those described above, and will not be repeated here.

The lithium salt is a lithium salt well known to those skilled in the art, and there is no special limitation. In the present invention, LiPF ₆ , LiBF ₄ , LiBOB, LiODFB, LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ , LiN One or more of (C ₂ F ₅ SO ₂ ) ₂ , LiCH ₃ SO ₃ and LiB(C ₂ O ₄ ) ₂ . The concentration of the lithium salt in the lithium-ion battery electrolyte is preferably 0.7-1.4 mol/L, more preferably 0.8-1.2 mol/L.

The solvent is a solvent known to those skilled in the art that can be used for the electrolyte, and there is no special limitation. In the present invention, it is preferably a non-fluorine solvent, more preferably selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, carbonic acid Methyl propyl ester, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, 1,2-dimethoxyethane, γ-butyrolactone, γ-valerolactone, tetrahydrofuran, 2 - One or more of methyl tetrahydrofuran, acetate, propionate, butyrate, and ethylene sulfite, preferably chain carbonate and cyclic carbonate, etc., with mixed viscosity less than or equal to 1mPa.s Solvents with low viscosity, such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, can obtain higher ion conductivity by using solvents with low viscosity. The mass of the solvent is preferably 1% to 80% of the mass of the lithium ion battery electrolyte, more preferably 60% to 80%.

The mass of the hydrofluoroether sulfone compound represented by formula (I) in the electrolyte of the present invention is preferably 0.01% to 60% of the mass of the lithium ion battery electrolyte, more preferably 0.1% to 40%, and more preferably 1% to 20% %.

The hydrofluoroether sulfone compound represented by the formula (I) added to the lithium-ion battery electrolyte of the present invention contains a hydrofluoroether group. First, the hydrofluoroether sulfone compound represented by formula (I) retains the advantages of high pressure resistance of sulfone compounds, which can improve the pressure resistance performance of the electrolyte, and is especially suitable for the needs of high-power lithium batteries; secondly, The hydrofluoroether group is beneficial to overcome the disadvantages of high melting point and viscosity of sulfone compounds, so that the electrolyte can be applied in a lower temperature environment, and the electrolyte has a higher conductivity; again, the formula (I) The hydrofluoroether sulfone compounds shown have good compatibility with common electrolyte solvents and lithium salts, and are easy to form a homogeneous solution; finally, the hydrofluoroether sulfone compounds shown in formula (I) have both hydrofluorine The advantages of ether compounds are beneficial to increase the flash point of the electrolyte and make the electrolyte have good flame retardancy.

In order to further illustrate the present invention, the following examples describe in detail the hydrofluoroether sulfone compounds provided by the present invention, their preparation methods, and lithium-ion battery electrolytes, wherein, Examples 1-3 are the synthesis of hydrofluoroether sulfone compounds , Examples 4-7 are the application research of electrolytes based on hydrofluoroether sulfone compounds.

The reagents used in the following examples are all commercially available.

Example 1

1.1 Add 161g (2mol) Cl-CH ₂ CH ₂ -OH to a 0.5L flask, add 28g (0.5mol) potassium hydroxide under stirring conditions, then replace the system gas with nitrogen three times, heat to 35°C, and stir Slowly add 100.8g (2.1mol) CH ₃ -SH into the flask dropwise under the condition of 100°C. During the dropping process, use a room temperature water bath to keep the temperature of the system between 30°C and 40°C. After the dropwise addition is completed, continue to stir at room temperature for 1h , The mixture was rectified under reduced pressure to obtain the product hydroxyethyl methyl sulfide with a purity of 99.9% and a yield of 84%.

1.2 Add 184g (2mol) of the hydroxyethyl methyl sulfide obtained in 1.1 to a 0.5L flask, and slowly add 128g (4mol) of hydrogen peroxide dropwise under vigorous stirring, and keep the reaction in a water bath at room temperature during the dropwise addition The temperature is between 20°C and 30°C. After the dropwise addition, stir overnight at room temperature and distill to obtain the crude product. The crude product is rectified to obtain hydroxyethyl methyl sulfone with a purity of 99.3%.

1.3 Add 248g (2mol) of hydroxyethylmethyl sulfone obtained in 1.2 to a 0.5L high-pressure reactor, add 28g (2mol) of potassium hydroxide under stirring conditions, seal the reactor, vacuumize, and replace the system gas with nitrogen Three times, vacuumize again, feed 0.1Mpa difluorochloromethane, heat to 60°C, intermittently feed difluorochloromethane, keep the pressure in the kettle at 0.6-0.7MPa, wait until the pressure of the reactor does not change, stop Reaction, the mixed material is washed with water, after phase separation, 10ml bromine is added to the organic phase, stirred at room temperature for 2h, then sodium thiosulfate solution is added to wash to neutrality, after phase separation, rectification obtains the formula (I- 1) The yield of the hydrofluoroether sulfone compounds shown is 68%.

The product hydroxyethyl methyl sulfide obtained in 1.1, the hydroxyethyl methyl sulfone obtained in 1.2 and the hydrofluoroether sulfone compound shown in formula (I-1) obtained in 1.3 were tested by nuclear magnetic resonance, Obtain its proton nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum, the results are as follows:

Hydroxyethyl methyl sulfide: ¹ HNMR (400MHz, CDCl ₃ ): δ=2.02(s,H,OH), δ=2.84(d,3H,CH ₃ ), δ=3.60(t,2H,CH ₂ ),δ=4.09(t,H,CH ₂ ); ¹³ CNMR (100MHz,CDCl ₃ ):δ=17.4(-CH ₃ ),δ=36.4(-CH ₂ -S-),δ=61.3(-CH ₂ -O-).

Hydroxyethylmethylsulfone: ¹ HNMR (400MHz, CDCl ₃ ): δ=2.84(s,3H,CH ₃ ), δ=3.58(t,2H,CH ₂ ), δ=3.93(t,2H,CH ₂ ),δ=6.51(t,H,CH); ¹³ CNMR (100MHz,CDCl ₃ ):δ=42.1(-CH ₃ ),δ=55.7(-CH ₂ -O-),δ=61.2(-CH ₂ -S-).

Hydrofluoroether sulfone compounds represented by formula (I-1): ¹ HNMR (400MHz, CDCl ₃ ):δ=2.84(s,3H,CH ₃ ),δ=3.58(t,2H,CH ₂ ),δ =3.93(t,2H,CH ₂ ),δ=6.51(t,H,CH); ¹³ CNMR (100MHz,CDCl ₃ ):δ=42.1(-CH ₃ ),δ=50.1(-CH ₂ -O- ), δ=58.7(-CH ₂ -S-), δ=161.2(-CH-).

Example 2

Add 248g (2mol) of hydroxyethylmethyl sulfone obtained in 1.2 to a 0.5L high-pressure reactor, add 28g (2mol) of potassium hydroxide under stirring conditions, seal the reactor, vacuumize, and replace the system gas with nitrogen three times , and then vacuumize, feed 0.1Mpa hexafluoropropylene, heat to 60°C, intermittently feed hexafluoropropylene, keep the pressure in the kettle at 0.3-0.4MPa, wait until the pressure of the reactor does not change, stop the reaction, and mix the material with water After washing and phase separation, add 10ml of bromine to the organic phase, stir at room temperature for 2h, then add sodium thiosulfate solution to wash until neutral, after phase separation, rectify to obtain 99.9% purity of formula (I-2) Hydrofluoroether sulfone compounds, the yield is 70%.

The hydrofluoroether sulfone compound represented by the formula (I-2) obtained in Example 2 was tested by nuclear magnetic resonance, and its hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum were obtained. The results are: ¹ HNMR (400MHz, CDCl ₃ ):δ=2.86(d,3H,CH ₃ ),δ=3.58(t,2H,CH2),δ=3.93(t,2H,CH2),δ=5.00(m,H,CH); ¹³ CNMR ( 100MHz, CDCl ₃ ):δ=42.1(-CH ₃ ),δ=47.9(-CH ₂ -O-),δ=59.0(-CH ₂ -S-),δ=101.8(-CF ₃ ),δ= 102.7 (-CF ₂ -), δ = 112.9 (-CHF-).

Example 3

Add 248g (2mol) of hydroxyethylmethyl sulfone obtained in 1.2 to a 0.5L high-pressure reactor, add 28g (2mol) of potassium hydroxide under stirring conditions, seal the reactor, vacuumize, and replace the system gas with nitrogen three times , then vacuumize, feed 0.1Mpa tetrafluoropropene, heat to 60°C, intermittently feed 200g (2mol) tetrafluoropropene, keep the pressure in the kettle at 0.3-0.4MPa, stop the reaction when the pressure of the reactor does not change anymore , the mixed material was washed with water, after phase separation, 10ml bromine was added to the organic phase, stirred at room temperature for 2h, then sodium thiosulfate solution was added to wash to neutrality, after phase separation, rectification obtained the formula (I-3 ) The hydrofluoroether sulfone compound shown in ) has a yield of 71%.

The hydrofluoroether sulfone compound represented by the formula (I-3) obtained in Example 3 was tested by nuclear magnetic resonance, and its hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum were obtained. The results are: ¹ HNMR (400MHz, CDCl ₃ ):δ=2.84(d,3H,CH ₃ ),δ=3.58(t,2H,CH ₂ ),δ=3.93(t,2H,CH ₂ ),δ=6.02(m,H,CH); ¹³ CNMR (100MHz, CDCl ₃ ): δ=42.1(-CH ₃ ), δ=47.6(-CH ₂ -O-), δ=59.0(-CH ₂ -S-), δ=109.4(-CHF ₂ ), δ=117.8(-CF ₂ -).

The following examples 4-7 are the application research results of the electrolyte solution based on hydrofluoroether sulfone compounds.

Electrolyte tests are as follows:

The melting point data of the synthesized new hydrofluoroether sulfone compounds adopts the freezing point test method, referring to GBASTMD6875-2003 and GB510-83 methods, to investigate the freezing point of different compounds, and the results are shown in Table 1. The viscosity of the compound was measured using a Brookfield rotational viscometer at 30°C and 60 rpm. The measuring range of the rotor used is 1-150mPa·sec.

Use the AC impedance test method to test the conductivity of the electrolyte. The probe of the test system is first calibrated with a standard aqueous sodium chloride solution in the frequency range of 10-100000 Hz, and then the electrochemical probe is put into the electrolyte for testing. The test temperature is at Between 20°C and 28°C, the test results are obtained through equivalent circuit fitting to obtain linear resistance. The test results are shown in Table 1.

The electrolyte was left to stand at 25°C for 5 hours, the state of the electrolyte was observed, and its compatibility was evaluated. The results are shown in Table 1.

The electrochemical oxidation stability test was carried out on the electrolyte. Electrochemical stability uses a three-terminal system with a salt bridge connecting the test sample chamber to the sample chamber with a reference electrode. The test uses a platinum electrode with a diameter of 1.6mm as the working electrode, and a platinum wire electrode as the counter electrode, both of which are inserted into the sample studio. Add 0.6ml of electrolyte solution to the sample studio, the reference electrode is silver wire, inserted into the propylene carbonate solution of 0.01mol/LLiPF ₆ , the reference studio and the test studio use propylene carbonate containing 1mol/LLiPF ₆ For the salt bridge connection, the porous glass material is used to separate the salt bridge from the sample chamber and the reference electrode chamber respectively. The electrochemical test uses a PAR273A electrochemical workstation, the metal wire is connected to the electrode, and it is left to stand until the open circuit voltage is stable. The working electrode voltage in the electrochemical workstation is set to the open circuit voltage, and the applied voltage is set from the open circuit voltage to 4.0V voltage, using Ag/Ag ⁺ electrode as reference electrode, record the relationship between current and voltage, when the current density is 1mA/cm ² , the results are shown in Table 2.

The flame retardant performance of the electrolyte is tested, and the self-extinguishing time (SET) is used to quantify the flame retardant effect. SET refers to the time consumed from ignition to self-extinguishing of 1ml of electrolyte evenly soaked in a fire-resistant cotton ball with a diameter of 0.5cm Time, the unit is s/ml. The self-extinguishing time of the electrolyte of Comparative Example 1 is set as SET0, and the self-extinguishing time of the electrolyte containing the sulfone additive is set as SET (as described in the literature JElectrochemSoc., 2003, 150 (2): A161-A169), then when ①When SET/SET0<0.1, the electrolyte is defined as flame retardant; ②When 0.1<SET/SET0<0.33, it is defined as near flame retardant; ③When SET/SET0>0.33, it is flammable. The results are shown in Table 2.

The battery cycle performance test is as follows:

The electrolyte was assembled into a button battery, the battery model was aluminum shell battery 2032, the positive pole was lithium cobalt oxide, the negative pole was natural graphite, and the diaphragm was Celgard brand polypropylene diaphragm. Carry out the discharge characteristic test on the button battery assembled above, adopt the Arbin battery tester, the cycle characteristic test condition of the battery: in the environment of 25 ℃, carry out constant current and constant voltage charging under the electric current value of 0.25mA and the voltage of 4.2V When the current is 0.1C, the battery is left to stand for 10 minutes, then discharged at a constant current to a final voltage of 2.7V at a rate of 1C, left to stand for 10 minutes, and charged and discharged for 10 cycles. The results of the cycle test are shown in Table 3.

The button battery assembled above was further tested for withstand voltage. Charge the battery with a constant current of 1C rate to 4.2V, then fully charge it with a constant voltage of 4.2V to a cut-off current of 0.1C, and then overcharge it at a rate of 1C for 2.5h to evaluate the overcharge withstand voltage performance of the battery. and explosions are invalid. The results are shown in Table 2.

Example 4

Methyl ethyl carbonate (EMC) and dimethyl ethylene carbonate (EC) were mixed as a solvent at a ratio of 65wt% and 35wt% by mass, and lithium hexafluorophosphate (LiPF ₆ ) was added with a lithium ion concentration of 1mol/L. Calculation of total liquid mass Add 5wt% of the hydrofluoroether sulfone compound represented by formula (I-1) prepared in Example 1, stir well at 25°C, and prepare lithium-ion battery electrolyte.

Example 5

Methyl ethyl carbonate (EMC) and dimethyl ethylene carbonate (EC) were mixed as a solvent at a ratio of 65wt% and 35wt% by mass, and lithium hexafluorophosphate (LiPF ₆ ) was added with a lithium ion concentration of 1mol/L. Calculation of total liquid mass Add 5wt% of the hydrofluoroether sulfone compound represented by formula (I-2) prepared in Example 2, stir well at 25°C, and prepare lithium-ion battery electrolyte.

Example 6

Methyl ethyl carbonate (EMC) and dimethyl ethylene carbonate (EC) were mixed as a solvent at a ratio of 65wt% and 35wt% by mass, and lithium hexafluorophosphate (LiPF ₆ ) was added with a lithium ion concentration of 1mol/L. Calculation of the total mass of the solution Add 5 wt% of the hydrofluoroether sulfone compound represented by the formula (I-3) prepared in Example 3, stir well at 25° C., and prepare the lithium-ion battery electrolyte.

Example 7

Methyl ethyl carbonate (EMC) and dimethyl ethylene carbonate (EC) were mixed as a solvent at a ratio of 65wt% and 35wt% by mass, and lithium hexafluorophosphate (LiPF ₆ ) was added with a lithium ion concentration of 1mol/L. Calculation of total liquid mass Add 10wt% of the hydrofluoroether sulfone compound represented by formula (I-1) prepared in Example 1, stir well at 25°C, and prepare lithium-ion battery electrolyte.

Comparative example 1

Methyl ethyl carbonate (EMC) and dimethyl ethylene carbonate (EC) were mixed as a solvent at a ratio of 65wt% and 35wt% by mass, and lithium hexafluorophosphate (LiPF ₆ ) was added with a lithium ion concentration of 1mol/L. °C and fully stirred to prepare the lithium-ion battery electrolyte.

Comparative example 2

Methyl ethyl carbonate (EMC) and dimethyl ethylene carbonate (EC) were mixed as a solvent at a ratio of 65wt% and 35wt% by mass, and lithium hexafluorophosphate (LiPF ₆ ) was added with a lithium ion concentration of 1mol/L. Calculation of the total mass of the solution Add 3wt% sulfolane (TMS), stir well at 25°C, and prepare the lithium-ion battery electrolyte.

Table 1 Lithium-ion battery electrolyte physical property test results

It can be seen from Table 1 that the addition of the sulfolane compound in Comparative Example 2 reduces the ionic conductivity of the electrolyte, so it is usually accompanied by the use of a co-solvent to ensure the uniformity of the electrolyte system and avoid a large loss of electrolyte. conductivity, while in Examples 4-7, the introduction of hydrofluoroether groups into hydrofluoroether sulfone compounds reduces its impact on the ionic conductivity of the electrolyte, thus proving that hydrofluoroether sulfone compounds improve compatibility of the electrolyte system. This result can be supported from the viscosity data of three hydrofluoroether sulfone compounds in the present invention and sulfolane in Comparative Example 2 in Table 1.

The static test shows that: due to the difference in the composition of the electrolyte, the introduction of sulfolane in Comparative Example 2 is likely to cause electrolyte stratification in the electrolyte, while the sulfone/fluoroether modified by fluoroether substitution does not occur in the static process. (Examples 4-7), so the introduction of fluoroether groups improves the solubility of sulfone compounds in the electrolyte. This can be explained by the melting point and viscosity of hydrofluoroether-based sulfone compounds. As can be seen from the melting point data in Table 1, the melting points of compounds I-1, I-2, and I-3 in the present invention are all at zero degrees under normal pressure. Below, far below the melting point of sulfolane at 27.8°C.

Table 2 Lithium-ion battery electrolyte pressure resistance, flame retardant performance test results

As can be seen from the data in Table 2, the test results of the three-electrode method show that the electrochemical oxidation of the cathode produces a higher cathode potential, indicating that the lithium ion battery electrolyte is more stable at a higher potential, especially the lithium ion batteries of Examples 4 to 7 of the present invention. The battery electrolyte has a higher oxidation potential, which proves that it has better pressure resistance. The further pressure test data of the whole button battery (as shown in Table 2) shows that the sulfone compound has a good effect on improving the battery voltage resistance, and none of the tested batteries showed combustion or explosion. At the same time, the introduction of the sulfolane in Comparative Example 2 and the sulfone/fluoroether additives in Examples 4-7, compared with the electrolyte in Comparative Example 1, significantly improved the flame retardancy of the electrolyte.

Table 3 Lithium-ion battery electrolyte cycle performance test results

The cycle capacity test results are shown in Table 3. The charge-discharge cycle test of the button battery confirms the application results of the electrolyte formulation of the present invention in lithium-ion batteries, that is, the introduction of hydrofluoroether groups can improve the traditional sulfone compounds (Comparative Example 2) influence on the electrochemical performance of the electrolyte.

In view of the comparative advantages of the above indicators, the battery device using the present invention to provide the electrolyte has shown excellent performance in output performance, especially in cycle stability and pressure resistance performance. These effects are all attributed to hydrogen Changes in structural and physical properties caused by the modification of sulfone compounds by fluoroether groups.

The examples cited above do not represent exhaustive combinations of application examples, but are non-limiting embodiments. In addition to the clear requirements for primary and secondary lithium battery electrolytes, normal formulation adjustments only address the requirements of individual indicators and have no specific impact on the versatility of the electrolyte.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (7)

1. a hydrogen fluorine ether sulfone compound, as shown in the formula (I):

（I）；

Wherein, R ₁for-CH ₃; R ₂for-CH ₂cH ₂-; R _ffor-CF ₂h.

2. the preparation method of a hydrogen fluorine ether sulfone compound according to claim 1, it is characterized in that, comprise: under the first catalyst action, by shown in the sulfone compound shown in formula (II) and formula (III) containing fluorine halide hybrid reaction, obtain the hydrogen fluorine ether sulfone compound shown in formula (I); Or under the second catalyst action, by the Fluorine containing olefine hybrid reaction shown in the sulfone compound shown in formula (II) and formula (IV), obtain the hydrogen fluorine ether sulfone compound shown in formula (I);

（I）；

（II）；

（III）；

（IV）；

Wherein, R ₁for-CH ₃; R ₂for-CH ₂cH ₂-; R _ffor-CF ₂h; X is halogen; Rf ₁and Rf ₂for fluorine-containing alkane or F; R ₃and R ₄for H, F, alkane or fluorine-containing alkane, and the Fluorine containing olefine shown in formula (IV) and R _fcarbon-chain structure identical, namely the Fluorine containing olefine shown in formula (IV) forms the R of the hydrogen fluorine ether sulfone compound shown in formula (I) after reacting with the sulfone compound shown in formula (II) _fsubstituting group.

3. a lithium-ion battery electrolytes, is characterized in that, comprising:

Lithium salts, the hydrogen fluorine ether sulfone compound shown in solvent and formula (I);

（I）；

Wherein, R ₁for-CH ₃; R ₂for-CH ₂cH ₂-; R _ffor-CF ₂h.

4. lithium-ion battery electrolytes according to claim 3, is characterized in that, the concentration of described lithium salts is 0.7 ~ 1.4mol/L.

5. lithium-ion battery electrolytes according to claim 3, is characterized in that, the quality of described solvent is 1% ~ 80% of lithium-ion battery electrolytes quality.

6. lithium-ion battery electrolytes according to claim 3, is characterized in that, the quality of the hydrogen fluorine ether sulfone compound described in described formula (I) is 0.01% ~ 60% of lithium-ion battery electrolytes quality.

7. lithium-ion battery electrolytes according to claim 3, it is characterized in that, described solvent is selected from one or more in NSC 11801, propylene carbonate, Methyl ethyl carbonate, methyl propyl carbonate, methylcarbonate, diethyl carbonate, ethylene carbonate, Texacar PC, 1,2-glycol dimethyl ether, gamma-butyrolactone, γ-valerolactone, tetrahydrofuran (THF), 2-methyltetrahydrofuran, acetic ester, propionic ester, butyric ester and glycol sulfite.